A video signal of a high dynamic range (HDR) has a luminance level range from 0% to 100%*N (N is a number larger than one) with respect to a video signal of a standard dynamic range (SDR) having a luminance level range of 0% to 100%. A camera which outputs an HDR video signal as a captured video signal is conventionally known (refer to, for example, Patent Document 1).
With the HDR video signal, it is difficult to correctly grasp a luminance level of each subject due to expansion in dynamic range. For example, even if the HDR video signal exceeding 1000% is displayed on a waveform monitor with a linear signal level, scale feeling of luminance is too wide to grasp a situation of the luminance level in a normal zone important as video, and on the other hand, in a case where a signal of a transmission format subjected to gradation compression processing by using an optical-electro transfer function (OETF) is displayed with a code as it is, a high luminance portion is compressed to be displayed on the contrary, so that it becomes difficult to grasp the correct luminance level.
Also, in a case of checking the luminance on a video monitor, since human vision has a logarithmic characteristic, for example, as compared to a difference in luminance change which may be recognized at 50% and 100% in the luminance level range of the SDR video signal, a difference in luminance change which may be recognized at 250% and 500% in the luminance level range of the HDR video signal is small and it is difficult to distinguish clearly.
Conventionally, it is suggested to detect a predetermined luminance level region from the SDR video signal, and combining a display signal for displaying the region with the SDR video signal to obtain an SDR video signal for display, thereby easily checking the predetermined luminance level region on a screen (refer to, for example, Patent Document 2).